Thermal storage system for use in connection with a thermal conductive wall structure

ABSTRACT

There is described a thermal storage system for transferring and storing heat in the ground, the thermal storage system comprising pumping means configured to circulate a working fluid, a heat exchanger, a supply output, a length of pipe, a return inlet and a thermally conductive ground engaging footing such that the pumping means circulates the working fluid through the length of pipe allowing heat transfer between the ground and the working fluid, the thermally conductive ground engaging footing thermally communicating with the ground.

FIELD OF THE INVENTION

The present invention relates to thermal storage systems adapted to store energy in the ground, absorb the stored energy from the ground and transfer the stored energy into a thermally conductive wall structure.

BACKGROUND OF THE INVENTION

Heating and cooling buildings consumes a large amount of energy. This is particularly the case in climates where there is a great disparity between maximum summer and minimum winter temperatures, as in much of North America, where it is necessary that buildings are cooled in the summer and heated in the winter.

Buildings are cooled and heated by a variety of means, including air conditioning units, electric heaters, wood stoves, forced air gas furnaces, and hot water or steam radiators. It is generally the case that a constant indoor temperature is desired depending on the external temperature. For example, room temperature (a temperature at which humans are generally accustomed for indoor living) is typically between 64-74° F. (approximately 18-23.5° C.), however local climate conditions may acclimatise people to higher or lower temperatures.

To minimize heat transfer between a building and its surrounding environment, various construction techniques have been developed which minimize the amount of energy required to maintain constant indoor temperatures. Examples of such techniques include designing and using building materials and insulation with high values of thermal resistance (also known as R-values), and employing air-flow heat exchangers which minimize the amount of heat lost to the external environment in the winter and reduce the amount of heat gained from the external environment in the summer.

Another way to improve the energy efficiency of a building is to make use of available geo-thermal energy. As is well known, the ground temperature below the frost line in much of North America is a relatively stable 55-56° F. on average (approximately 13° C.) throughout much of North America, ranging from around 41° F. (5° C.) in northern climates to about 71° F. (21.6° C.) in southern climates.

Ground-source heat pumps are one well known type of technology which take advantage of this physical phenomenon. Heat pumps typically have a series of heat exchanging coils buried in the ground below the frost line. In warm summer months, water can be cooled to the ground temperature when circulating through these coils. This cooled water can then be circulated in radiators located inside the building to cool the interior space, among other applications. In a similar way, a building can be heated in the winter by warming the water in the heat exchanging coils.

However, there has been a lack of construction technology specifically designed to take advantage of the fact that the ground surrounding and underlying a building can be used as a heat sink in the summer and a heat source in the winter.

Furthermore, there has also been a lack of construction technology adapted to store abundant heat energy in the summer for use as a heat source in the winter months.

Therefore, there is a need for building structures and techniques which reduce energy consumption by using the ground for heat storage in the summer such that the ground can be as a source of heat in the winter.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a thermal storage system for storing heat in the ground beneath a building such that the stored heat can be transferred to a thermally conductive ground engaging footing. Therefore, in at least one embodiment, the thermally conductive ground engaging footing can form the below grade foundation of a vertical wall structure that is contemplated to absorb the stored heat from the ground through the footing into the interior structure of the wall. This arrangement can reduce the heating costs of a building by raising the internal temperature of the vertical wall structure in the winter.

In at least one embodiment, the thermal storage system of the present invention can be used to cool the ground beneath a building by conducting heat from the vertical wall structure through a thermally conductive ground engaging footing into the ground. This arrangement can reduce the cooling costs of a building by lowering the internal temperature of the vertical wall structure in the summer.

In at least one embodiment of the present invention, there is provided a thermal storage system which includes a longitudinally extending ground engaging footing, the footing extending horizontally through the ground below the frost level and having an upper surface and a lower surface, pumping means configured to circulate a working fluid, a heat exchanger, the heat exchanger configured to transfer heat between the working fluid and the outside environment, the heat exchanger fluidly communicating with the pumping means, at least one supply outlet, the at least one supply outlet fluidly communicating with the heat exchanger, at least one length of pipe, the at least one length of pipe fluidly communicating with the supply input, the at least one length of pipe thermally communicating with the ground under the longitudinally extending ground engaging footing, at least one return inlet, the at least one return inlet fluidly communicating with the at least one pipe such as the pumping means circulates the working fluid through the heat exchanger to the at least one length of pipe by way of the supply outlet, the working fluid experiencing heat transfer with the at least one length of pipe, the at least one length of pipe experiencing heat transfer with the ground, the working fluid returning to the pumping means by way of the return inlet.

In at least one embodiment of the present invention, there is provided a method of storing heat in the ground beneath a building which includes the steps of burying at least one length of pipe in the ground below the frost level, the at least one length of pipe configured to receive a working fluid from a heat exchanger, the at least one pipe thermally communicating with the ground below the frost level, forming a longitudinally extending footing in the ground above the at least one length of pipe, supporting a vertical wall on the footing, the vertical wall extending upwardly from the footing to a selected height above grade, sheathing the vertical wall in insulation, lacing the interior of the vertical wall and the footing with thermally communicating heat conducting members, at least some of the heat conducting members extending outwardly from the footing into the ground a selected distance to facilitate heat transfer between the ground and the vertical wall.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described in greater detail and will be better understood when read in conjunction with the following drawings in which:

FIG. 1 is a side elevational transversely cross-sectional view of one embodiment of a conductive wall structure for use in connection with the present invention;

FIG. 2 is a side elevational transversely cross-sectional view of another embodiment of a conductive wall structure for use in connection with the present invention;

FIG. 3 is a side elevational view showing one embodiment of the above ground connection of conductive elements within a wall for use in connection with the present invention;

FIG. 4 is a side elevational transversely cross-sectional view of one embodiment of a conductive wall structure for use in connection with the present invention;

FIG. 5 is a side elevational transversely cross-sectional view of one embodiment of a conductive wall structure for use in connection with the present invention;

FIG. 6 is a plan view of one embodiment of the thermal storage system of the present invention; and

FIG. 7 is a cross sectional view one embodiment of the thermal storage system of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As is well known, the temperature inside the ground below the frost line is a relatively stable 55-56° F. on average (approximately 13° C.) throughout much of North America, ranging from around 41° F. (5° C.) in northern climates to about 71° F. (21.6° C.) in southern climates. This temperature is above the normal ambient atmospheric temperature during northern winters and below normal ambient atmospheric temperatures during the summer in most places. This delta temperature has therefore been previously used to effect a heat transfer that warms in the winter and cools in the summer. The heat transfer however has typically been accomplished using conventional heat exchangers that transfer heat from one fluid to another by means of direct thermal coupling or airflow.

The present invention seeks to store energy in the ground beneath a building and use this stored heat to heat a wall structure through direct thermal conduction. Alternatively, the present invention can be used to cool the ground beneath a building such that a wall structure can be cooled through direct thermal conduction with the cooled ground beneath the building.

With reference to FIG. 1, an exemplary wall structure 10 adapted to use heat energy stored in the ground in the manner described below generally comprises a ground engaging concrete footing 15, a vertical wall 25 and an envelope of insulation 40 that completely sheaths wall 25 except for the wall's lowermost surface 26 where it connects with footing 15. Any openings in the wall for windows, doors and the like will similarly and preferably be lined with insulation.

The ground 2 itself is the heat source for the present wall structure during the heating season so footing 15 is the primary thermal interface between the ground and wall 25 where the ground's energy is picked up.

Footing 15 will advantageously be positioned at least three feet below the local frost level, this level being the depth to which the ground will normally freeze in the coldest part of the winter, and is a poured concrete slab having a preselected transverse width of preferably at least 24 inches. Smaller widths are possible but testing shows that better results are obtained at 24 inches or greater. The footing's height will preferably be at least 8 inches but again this is variable. As will be appreciated, local building codes and engineering requirements will dictate the footing's minimum structural and dimensional requirements but the present invention may require that those minimums be exceeded.

The concrete for the footing will be gravel type having a minimum thermal conductivity of 2.0 W/mK. As will be known in the art, some concretes are not thermally conductive and the use of these for the footing is preferably avoided. Avoided concretes include lightweight, pumice powder, cellulose, isolation or slag concretes, all of which have significantly lower thermal conductivity. Applicant has found that the conductivity in the footing is increased using gravel having a 19 millimetre average particle size.

To increase heat transfer from the ground to the footing, the interface 5 between the two may optionally be laced with galvanized steel dowels 50. These can be laid in a cross-hatched pattern or linearly in the longitudinal direction of the footing on 16 inch centers, although other spacings are contemplated as well. Other patterns and configurations are possible, the idea simply being to facilitate heat transfer from the ground to the footing by means of these conductive elements. More effective means of promoting heat transfer from the ground to the footing are described below.

Within the footing itself, there will normally be reinforcing bar (rebar) in any event for strengthening the slab as necessary to meet local code and engineering requirements. Advantageously, the rebar will include a plurality of longitudinally extending continuous runs of steel 15M(#5) rebar 55. This rebar is normally located below the footing's horizontal center line as shown most clearly in FIG. 1. The typical placement of the rebar will be approximately 2 inches above the bottom of the footing. The rebar can be placed above or at the center line but for structural reasons, this is considered undesirable. Each run of rebar 55 will extend continuously and preferably without gaps or breaks from one end of the footing to the other and for a 24 inch wide footing, there will preferably be at least three of such runs.

A continuous and longitudinally extending strip 57 of heat conducting material is positioned on the footing's upper surface 29 in the position shown most clearly in FIG. 1 offset relative to vertical wall's 25 center line. As seen in FIG. 1, the strip is located on top of the footing adjacent the wall's interior surface 24. In one embodiment constructed by the applicant, strip 57 is a two inch wide 24 gauge piece of galvanized steel anchored in place by spaced apart galvanized steel dowels 58 that pass downwardly through the footing, through the soil-footing interface 5 and then into the soil itself to a predetermined depth, preferably a minimum of 4 inches.

The next element in the ground source pickup is a series of vertically oriented, longitudinally spaced apart dowels 52 that extend from a point in the footing close to but preferably not in contact with the ground/soil interface 5, vertically upwardly through the remainder of the footing and into the lower reaches of wall 25 as shown most clearly in FIG. 1. These dowels are preferably located along the wall's center line and contact the edge 56 of conductive strip 57 where the dowels emerge from the footing for thermally conductive contact with the strip. The dowels can be welded, wired to or simply biased against strip 57 for heat transfer therebetween. In one embodiment constructed by the applicant, dowels 52 are 10M(#4) steel rebar, are horizontally spaced apart at minimum 16 inch centers and each extends into wall section 25 by approximately 16 inches. This length of penetration can vary, but 16 inches has been found to provide good results.

In the alternative to using the two sets of dowels 52 and 58, dowels 58 can be eliminated if dowels 52 are downwardly elongated to penetrate through the footing and into the ground to a predetermined depth, preferably at least 4 inches as shown in FIG. 2. The dowels would then need to be corrosion protected, and the use of galvanized steel would be preferred in this application.

The next element of the wall system is to provide a conductive path for the heat absorbed from the ground into wall 25 itself.

With reference to FIG. 1 again, this can be accomplished in a number of ways with one particularly preferred configuration being shown in the drawing. This configuration is essentially a grid or grids of conductive elements located inside wall 25.

The conductive elements of the grid are center line vertical conductors 80, horizontal center line conductors 85, off center vertical conductors 90, off center horizontal conductors 95 and horizontal continuity links 100.

Starting from the bottom of wall 25, off center conductors 90 extend upwardly from strip 57 to a point in wall 25 a selected vertical distance above grade. The lower end of each conductor is biased, welded or otherwise connected to strip 57 so the two are thermally connected for heat transfer purposes. Conductors 90 are located off center of the wall more towards its interior surface 24 to better isolate the conductors from the wall's cold outer surface 26 and any moisture that might penetrate the wall from the ground. Off center horizontal conductors 95 are tied or otherwise connected to vertical conductors by means of metal wire, clips or other means known in the art, the only requirement being that all intersections between the conductors be thermally conductive. As seen in FIG. 1, conductors 95 can be located on alternating sides of vertical conductors 90 or the horizontal conductors can be located on both sides of the vertical conductors as shown in FIG. 3.

Above grade, vertical conductors 80 can be positioned along the wall's vertical center line with the horizontal conductors 85 connected thereto in the same manner described above with respect to conductors 90 and 95.

A thermally conductive continuity link 100 connects lower conductors 90/95 to upper conductors 80/85. The link can be made up of short sections of the same conductors used for conductors 80, 85, 90 and 95 that thermally connect the upper and lower conductor grids together for heat transfer therebetween.

The conductors in wall 25 can be lengths of 10M(#4) steel reinforcing bar connected together in a preferably minimum 16 inch on center grid in both the horizontal and vertical directions. As will be appreciated, the conductors can perform double duty as reinforcing for the wall itself in accordance with local building code requirements and engineering specifications.

As will be seen in FIG. 1, the conductive grids extend from the bottom of wall 25 to near its top where the wall includes a sill plate 160 which will normally be a piece of dimensional lumber for the connection of joists, rafters, trusses or other structural elements to the wall. To prevent heat loss, a thermal break (not shown) can be provided at the interface of sill plate 160 and the trusses etc. This can be achieved by using a rigid non-thermally conductive material such as polycarbonate insulation between the trusses etc. and the sill plate.

Unlike footing 15, wall 25 is preferably poured from low thermal conductivity concrete to minimize heat transfer from its warm side to its cold side. Again the concrete can be gravel concrete but using gravel having a 12 millimetre average diameter is preferred.

As mentioned above, the wall from footing 15 all the way to its top should be monolithically sheathed in insulation 40 so that there are no significant breaks, gaps or openings in the coverage. The insulation can be a foam type such as expanded polystyrene readily available from most building supply stores and which is manufactured in sheets. The foam insulation can be connected to the wall by means of adhesives, staples or any other means known in the art that are not thermally conductive. Whichever means are chosen should obviously minimize thermal conduction from the wall/insulation interface to the insulation's outer surface. For good results, the insulation on the wall's vertical surfaces should be minimum R9, and R25 along the wall's upper edge 27.

Any openings in wall 25 for doors, windows or other features should preferably be lined with slabs of foam or other equivalently insulative materials to prevent thermal loss around the opening edges. Equivalent materials can include for example the use of low expansion insulating foams injected into the peripheral gaps between the window/door and the wall openings to secure the windows/doors in place. The use of metal fasteners between the windows/doors and the concrete of wall 25 is preferably avoided to minimize thermal conduction.

Advantageously, the upper surface 29 of footing 15 on the side of interior wall surface 24 is also insulated for example by a piece of foam 31 (preferably minimum R8) to insulate the footing from the building's floor slab.

Wall 25 will itself extend from the building's footings 15 up to its eaves. It is preferable that wall 25 has minimal openings and penetrations as it is important to maintain as monolithic a construction as possible to maintain the integrity of the wall's thermal conductivity.

In operation, it has been found that a wall structure as described above conserves heat within the building and significantly reduces heat transfer from the inside to the outside in winter and from the outside to the inside in the cooling season. As will be appreciated, during the cooling season, the wall acts in reverse to its operation as described above in relation to the heating season and will conduct heat from above grade to the ground below grade.

With reference to FIG. 4, another embodiment of the present invention is illustrated wherein vertical conductor 90 is aligned with dowel 58. Therefore, dowel 58 is in thermal communication with conductive strip 57. Dowels 58 project through concrete footing 15 and through the soil-footing interface 5 into ground 2 as described above with reference to FIGS. 1 and 2. This construction eliminates the need for dowels 52.

With reference to FIG. 5, another embodiment of the present invention is illustrated wherein vertical conductors 80 extend vertically through wall 25, such that vertical conductors 90 are not required. Typically, each vertical conductor 80 will be located along the centre line of wall 25 towards inner wall surface 24 in the location of conductors 90 in FIGS. 1 and 4. In this embodiment, vertical conductor 80 is aligned with dowel 52. Therefore, dowel 52 is in thermal communication with conductive strip 57 and dowel 52 projects through concrete footing 15 and through the soil-footing interface 5 into ground 2 as described above in connection with FIGS. 1 and 2. This embodiment eliminates the need for two sets of dowels 52 and 58. Structurally however, this embodiment may not comply with local building codes that require below grade rebar to be located towards the wall's inner (tension) side due to the pressure of the earth on the wall's outer side. As well, in this embodiment, as in the others described above, the conductors in wall 25 can be thermally connected directly or indirectly to the dowels that extend into or through the footing which can eliminate the need for conductive strip 57 in some instances.

Thermal Storage System

The present invention also relates to a thermal storage system 200 that will now be described with reference to FIGS. 6 and 7, in which like elements have been identified using like numerals. Storage system 200 is designed to operate in tandem with thermally conductive wall structure 10, embodiments of which have been described above. The thermal storage system 200 increases the efficiency of wall structure 10 by providing a heat sink which can store heat during the warm summer months for use as an additional heat source in the cooler winter months.

Referring now to FIG. 6, a preferred embodiment thermal storage system 200 is illustrated wherein a working fluid is pumped through underground piping 202 for heat transfer purposes by means of a pumping means such as pump 220. Pump 220 can be any suitable pump for the purpose such as, for example, a progressive cavity, positive displacement, reciprocal or centrifugal pump. Pump 220 will typically be electrically powered, however it is also contemplated that the pump could be powered by an internal combustion engine or any other suitable prime mover.

The working fluid can be water, glycol, a mixture of glycol and water, or any other fluid that has suitable environmental and heat transfer properties for use in the present invention.

In the embodiment shown in FIGS. 6 and 7, which is configured and dimensioned for climatic conditions prevailing in Western Canada, underground piping 202 consists of two concentric loops of pipe or conduit 204 and 206 buried beneath a building's floor slab 300. The horizontal spacing between the conduits is about 12 inches but this spacing can be increased or decreased. Measured from the mid point between the two conduits, they are inset approximately 30″ on all sides from the inner edge of footing 15 as it follows the floor plan of the building, as can be seen most clearly in FIG. 6. As will be discussed below, this distance will vary depending on a number of factors including climatic conditions. As well, the layout of underground piping 202 can take a different shape such as an ellipse, square or circle and could be larger or smaller relative to the perimeter of the floor plan of the building depending on climactic conditions. Furthermore, underground piping 202 could take a variety of shapes other than simple loops such as crisscrossed patterns or concentric spiral loops underneath building slab 300.

It is also contemplated that a single loop of piping could be buried beneath slab 300, and furthermore three or more loops of piping could also be employed in the present invention.

In one embodiment contemplated by the applicant, underground piping 202 is typically buried approximately 32″ beneath the lower surface 301 of slab 300, however underground piping 202 could be located deeper or shallower depending on climactic conditions, and soil thermal conductivity.

Underground piping 202 can be constructed of schedule 40 stainless steel tubing, however pipes of different thickness and constructed of different materials are also contemplated. For example, climactic conditions permitting, underground piping could be constructed of plastic or other metals, such as titanium, galvanized steel, cast iron or aluminum.

Conduit 204 has an inlet end 208 and an outlet end 209. Similarly, conduit 206 has an inlet end 210 and an outlet end 211. These ends are connected to a manifold 215 for the supply and return of working fluid from pump 220. Specifically, working fluid is pumped from pump 220 and enters conduits 204 and 206 through their inlet ends 208 and 210 respectively via manifold 215. After circulating through conduits 204 and 206, the working fluid leaves the conduits through their outlet ends 209 and 211, respectively, into manifold 215 where the return flows are combined for flow back to pump 220. In embodiments with more or less than two loops, there will be a corresponding number of supply inlets and outlets and an appropriately modified manifold.

In at least one embodiment, the working fluid is pumped through a heat exchanger 230 where the fluid can be either cooled or heated depending on the exterior ambient temperature and the availability of solar radiation. Heat exchanger can simply be a series of radiation absorbent plastic or metal pipes located on the roof of the building, or it could be a more sophisticated model including those which could recover waste heat emitted from the building and or sources from within the building. Heat exchanger 230 can be a solar collector or any other type of exchanger that is suitable for the use in connection with the present invention. Heat exchanger 230 can be an open loop or closed loop configuration.

The heat exchanger can be located either upstream or downstream from pump 220, such that it can receive either depressurized return working fluid before it is pressurized by pump 220 or it can receive pressurized working fluid after it has been pressurized by pump 220 depending on the thermodynamic requirements of the application.

Therefore, in one embodiment of the present invention, the working fluid is pressurized by pump 220 and supplied to heat exchanger 230 so that in the warm summer months, the heat exchanger transfers heat from the environment into the working fluid. Warmed working fluid is then circulated to underground piping 202 in the manner described above, causing the temperature of the soil in a heating zone 255 surrounding the piping within a radius 260 to rise as the warmed working fluid continuously circulates.

As will be seen, the radius 260 of heating zone 255 is selected so that from the mid point between pipes 204 and 206, the zone ideally reaches but does not significantly overlap footings 15 so that there is minimal heat transfer to the thermal walls during the cooling season. Obviously, it is not possible to precisely control the size of heating zone 255 due to fluctuations in solar radiation, soil type and density, the presence of ground water and other factors, but for any given geographic area, historical temperature and climatic records and soil measurements can be used to calculate the placement of pipes 204 and 206 with reasonable accuracy. In the example shown in FIG. 7, which is based on conditions prevailing in western Canada, radius 260 will be approximately 44 inches or 1.1 metres.

In other words, in western Canada, there are, on average, enough days having an above ground temperature in excess of ground temperature to heat a zone having a radius 260 of approximately 44″ inches. In geographic areas having more warm days, this radius will be greater and conversely, in colder climates having fewer warm days, the radius will be smaller.

If preferred, temperature sensors can be strategically placed to read soil temperatures and to transmit signals based on the temperatures to actuators to discontinue the circulation of working fluid if and when zone 255 begins to encroach on footings 15.

To contain the heat beneath the building during the heating season, it is preferred that slab 300, rather than being a typical reinforced poured concrete floor, is instead an insulating layer. To this end, slab 300 can be constructed in a number of ways that will be apparent to those skilled in the art. In a preferred embodiment, slab 300 consists of a layer of gravel e.g. 40 millimeter) compacted to a thickness equal to the thickness of footing 15, which in the example given above, is 8 inches, topped by a 4 inch thick covering 270 of expanded polystyrene foam insulation. Additional 2 inch thick strips 275 of EPS insulation can be embedded in the gravel directly above conduits 204 and 206, the width of the strips being selected to intersect the radius 260 of heating zone 255 at points 261 and 262. As will also be seen in FIG. 7, top dead center of radius 260 will intersect with the upper surface 271 of EPS layer 270.

In this way the present invention provides a means for storing heat under building slab 300. Once the weather turns cooler in the fall and winter, this stored heat, which will migrate towards the cooler ground around footings 15, can be used to heat wall structures 10, offering a reduction in energy input for heating and associated reduction in energy costs during the winter months.

It is contemplated that at certain times of the year the system may not be as thermodynamically effective, as the temperature difference between the soil under the building and the ambient environmental temperature may be negligible. Therefore, in at least one embodiment, valve 214 is provided so that circulation of the working fluid can be slowed or halted when climactic conditions dictate or when system maintenance is necessary. The valve can include an outlet for example to replenish, drain or replace the working fluid. A user can monitor the system and when it is determined that the climactic conditions are not ideal for running the thermal storage system 200 in connection with the wall structure 10, the valve can be closed off. Furthermore, two valves can be provided, one upstream and one downstream of pump 220, so that the pump can be effectively “locked out” for maintenance or replacement.

In another embodiment, the present invention can be configured such that working fluid is glycol or a glycol-water mix that does not freeze in winter temperatures. In this embodiment, the system can be operated towards the end of the winter months to cool the soil beneath the building by circulating the working fluid to heat exchanger 230 when ambient environmental temperatures are colder than the soil temperature beneath the building. In this way, when working fluid passes through heat exchanger 230, heat will be transferred from the working fluid and dissipated by heat exchanger 230 so that the temperature of working fluid will decrease and the soil surrounding underground piping 202 will be cooled. In this arrangement, the cool ground can be used to cool wall structure 10 and reduce energy input for cooling and associated energy costs in the summer months.

Example

By way of example, the thermal storage system of the present invention was tested using the following input parameters:

Variable Value Unit Comments soil thermal conductivity 1.5 W/mK This value is fixed and estimated for dry soil pipe thermal conductivity 0.51 W/m · K This value is fixed and known for pipe selected inside pipe temperature 80 ° C. This value is fixed and known desired ground temperature 23 ° C. This value is chosen as a set point inside pipe radius 0.013 m This value will depend on pipe selection outside pipe radius 0.019 m This value will depend on pipe selection and is selectable and variable distance from pipe to 1.119 m This value is chosen by installing engineer and footing will depend on application maximum volumetric 2500000 J/m³ · K This value is fixed and estimated for dry soil specific heat of soil minimum volumetric 2000000 J/m³ · K This value is fixed and estimated for dry soil specific heat of soil specific heat of working 3558.8 J/kg · K This value is known for this working fluid fluid (50-50 water/glycol mix) density of working fluid (50-50 1041 kg/m³ This value is known for this working fluid water/glycol mix) conductive heat transfer Calculate W/m This value is calculated based on system temperature loss/meter of Calculate C./m This value is calculated based on system pipe mass flow rate Calculate kg/sec This value is calculated based on system desired soil length 37 m This will depend on building desired length of 74 m This is based on a system with two loops underground piping

Based on the above input parameters, the skilled person in the art can now calculate the conductive heat transfer, the temperature loss from the input of the working fluid to the return of the working fluid, and the necessary mass flow rate for the system, using heat transfer and thermodynamic calculations known in the art, for proper configuration of the system, including the depth the conduits 202 are buried below the lower surface 301 of slab 300, and the horizontal spacing or inset of the conduits from the inner edge of footing 15.

Thermal storage system 200 can be retrofitted to an existing structure by trenching around its periphery for installation of conduits 204/206, or as the case might be, and an insulating barrier over the conduits to perform the function of slab 300 and EPS layer 270.

The above-described embodiments of the present invention are meant to be illustrative of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications, which would be readily apparent to one skilled in the art, are intended to be within the scope of the present invention. The only limitations to the scope of the present invention are set out in the following appended claims. 

1. A thermal storage system for a building having a peripherally extending thermally conductive wall structure comprising: a footing disposed in the ground below grade; a vertical wall supported on and extending longitudinally in the direction of the footing; the vertical wall extending upwardly from the footing above grade to a predetermined height; conduit means disposed in the ground a predetermined distance beneath and interiorly of said footing; means for circulating a working fluid through said conduit means; and means for transferring heat to or from said working fluid wherein the ground around said conduit means is respectively either heated or cooled for heat transfer between the heated or cooled ground and said footing and the wall structure supported thereon.
 2. The thermal storage system of claim 1 wherein said conduit means comprise one or more loops of tubing for the flow of said working fluid therethrough.
 3. The thermal storage system of claim 2 wherein each of said one or more loops of tubing has an inlet end and an outlet end in fluid communication with said means for circulation.
 4. The thermal storage system of claim 3 wherein said means for circulation is a pump.
 5. The thermal storage system of claim 4 wherein said means for transferring heat is a heat exchanger.
 6. The thermal storage system of claim 1 wherein said predetermined distance is the radius of a zone around said conduit means that, for a given thermal input, will extend from the conduit means to a portion of said footing closest to said conduit means.
 7. The thermal storage system of claim 6 wherein said predetermined distance will vary at least in part depending upon the number of days in the geographic location where the building is located where the temperature above the ground exceeds the temperature of said z one and said conduit means.
 8. The thermal storage system of claim 7 wherein said building includes a floor structure circumscribed at least in part by said footing, said floor structure providing an insulating layer that acts as a thermal barrier between the interior of said building and the heated or cooled g round in said z one around the conduit means.
 9. The thermal storage system of claim 8 wherein said floor structure comprises a first and second layers of insulating material.
 10. The thermal storage system of claim 9 wherein said first insulating material is compacted gravel.
 11. The thermal storage system of claim 10 wherein said second layer is a rigid foam insulation disposed above said compacted gravel.
 12. The thermal storage system of claim 11 wherein the thickness of said compacted gravel is substantially equal to the vertical thickness of said footing.
 13. The thermal storage system of claim 12 wherein said layer of compacted gravel has an upper surface and a lower surface, said upper surface including therein insulation situated between the points where said radius of said z one around said conduit means intersects said upper surface of said layer of compacted gravel.
 14. A thermal storage system comprising: a longitudinally extending ground engaging footing, said footing extending horizontally through the ground below the frost level and having an upper surface and a lower surface; pumping means configured to circulate a working fluid; a heat exchanger, said heat exchanger configured to transfer heat between said working fluid and the outside environment, said heat exchanger fluidly communicating with said pumping means; at least one supply outlet, said at least one supply outlet fluidly communicating with said heat exchanger; at least one length of pipe, said at least one length of pipe fluidly communicating with said supply output, said at least one length of pipe thermally communicating with the ground under said longitudinally extending ground engaging footing; and at least one return inlet, said at least one return inlet fluidly communicating with said at least one pipe wherein said pumping means circulates said working fluid through said heat exchanger to said at least one length of pipe by way of said supply outlet, said working fluid experiencing heat transfer with said at least one length of pipe, said at least one length of pipe experiencing heat transfer with the ground, said working fluid returning to said pumping means by way of said return inlet.
 15. The thermal storage system of claim 14, said thermal storage system further comprising: a vertical wall, said wall extending vertically above grade from said footing and longitudinally along said footing, said wall having a lower surface, an upper surface, an interior surface and an exterior surface, said lower surface abutting said footing; a thermally conductive strip, said strip longitudinally positioned on the upper surface of said footing, said strip being located between the upper surface of said footing and the lower surface of said vertical wall; an insulating sheath, said sheath enveloping the interior, exterior and upper surfaces of said vertical wall; a first plurality of thermally conductive members disposed inside said vertical wall to be in thermal communication with one another, at least some of said members being in contact with said thermally conductive strip for heat transfer therebetween; and a second plurality of thermally conductive members disposed in said footing to be in thermal communication with said thermally conductive strip for heat transfer therebetween, at least some of said second plurality of thermally conductive members extending downwardly through the lower surface of said footing into the ground a selected distance.
 16. The thermal storage system of claim 15, said thermal storage system further comprising: a vertical wall supported on and extending longitudinally in the direction of the footing, the vertical wall extending upwardly from the footing above grade to a predetermined height, and having upper, lower, interior, exterior and end surfaces; a sheath of insulation for enveloping said vertical wall's upper, end, interior and exterior surfaces; and thermal conductors disposed in said vertical wall to be in thermal communication with one another, at least some of said conductors extending outwardly from said footing into the ground, the thermal conductors facilitating heat transfer between the ground and the vertical wall.
 17. The thermal storage system of claim 16, wherein said pumping means are selected from the group consisting of: a progressive cavity pump, a positive displacement pump, a reciprocal pump and a centrifugal pump.
 18. The thermal storage system of claim 17, wherein said heat exchanger is a solar heat exchanger.
 19. The thermal storage system of claim 18, wherein said heat exchanger recovers waste heat fed from one or both of a building and heat emitting sources associated therewith.
 20. The thermal storage system of claim 19, wherein said heat exchanger is located downstream from said pumping means.
 21. The thermal storage system of claim 20, further comprising a valve located downstream of said heat exchanger.
 22. The thermal storage system of claim 21, further comprising a first lockout valve and a second lockout valve, said first lockout valve located upstream of said pumping means and said second lockout valve located downstream of said pumping means.
 23. The thermal storage system of claim 15, wherein said first plurality of thermally conductive members form one or more grids in said vertical wall.
 24. The thermal storage system of claim 23, wherein said one or more grids comprise vertically and horizontally arranged thermally conductive members, said vertically and horizontally arranged members being in thermal contact where they intersect for heat transfer therebetween.
 25. The thermal storage system of claim 24, wherein said one or more grids comprise a first grid disposed in said vertical wall proximal the interior surface thereof, said first grid extending vertically from said thermally conductive strip to a point at grade or to a selected distance above grade.
 26. The thermal storage system of claim 25, wherein said one or more grids comprise a second grid disposed in said wall structure approximately equidistant between said interior and exterior surfaces thereof, said second grid extending vertically from adjacent an upper edge of said first grid to a point just below said vertical wall's upper surface.
 27. The thermal storage system of claim 26, wherein said first and second grids are thermally linked together for heat transfer therebetween.
 28. The thermal storage system of claim 15, wherein said second plurality of thermally conductive members includes a set of dowels horizontally spaced apart in the longitudinal direction of said footing, each of said dowels extending vertically from a point a selected distance above said footing's lower surface to a point a selected distance into said vertical wall, each of said dowels contacting said thermally conductive strip for heat transfer therebetween
 29. The thermal storage system of claim 15, wherein said second plurality of thermally conductive members includes a set of dowels horizontally spaced apart in the longitudinal direction of said footing, each of said dowels extending vertically downwardly from contact with said thermally conductive strip, through said footing and into the ground by a selected distance.
 30. The thermal storage system of claim 15, wherein said vertical wall is constructed from low thermal conductivity concrete.
 31. The thermal storage system of claim 15, wherein said footing is constructed of thermally conductive concrete with a minimum thermal conductivity of 2.0 W/mK.
 32. The thermal storage system of claim 15, wherein said footing additionally comprises at least one longitudinally aligned thermally conductive member extending continuously from one end of said footing to the other.
 33. The thermal storage system of claim 15, wherein said insulating sheath is constructed of a material with an insulation value of at least R9 along the interior and exterior surfaces of said vertical wall and an insulation value of at least R25 along the upper surface of said vertical wall.
 34. The thermal storage system of claim 15, wherein said footing is located at least three feet below said frost level.
 35. The thermal storage system of claim 32, wherein said first and second plurality of thermally conductive members and said longitudinally aligned thermally conductive member are metallic rods.
 36. The thermal storage system of claim 35, wherein said metallic rods reinforce said footing and said vertical wall.
 37. The thermal storage system of claim 16, wherein said thermal conductors include a first plurality of thermally conductive members disposed inside said vertical wall in thermal communication with one another.
 38. The thermal storage system of claim 37 wherein said thermal conductors include a second plurality of thermally conductive members disposed in said footing, at least some of second plurality of thermally conductive members extending outwardly from said footing into the ground a selected distance, said first and second plurality of thermally conductive members being in thermal communication for heat transfer therebetween.
 39. The thermal storage system of claim 38 wherein said thermal conductors include a thermally conductive strip disposed on said footing and extending longitudinally therealong, said thermally conductive strip being disposed between the footing and the vertical wall's lower surface.
 40. The thermal storage system of claim 39 wherein at least some of said first and second plurality of thermally conductive members contact said thermally conductive strip for heat transfer therebetween and to thermally connect said first and second pluralities of thermally conductive members.
 41. The thermal storage system of claim 40, wherein said first plurality of thermally conductive members form one or more grids in said vertical wall.
 42. The thermal storage system of claim 41 wherein said one or more grids comprise vertically and horizontally arranged thermally conductive members, said vertically and horizontally arranged members being in thermal contact where they intersect for heat transfer therebetween.
 43. The thermal storage system of claim 42, wherein said one or more grids comprise a first grid disposed in said vertical wall proximal the interior surface thereof, said first grid extending vertically from said thermally conductive strip to a point at grade or a selected distance above grade.
 44. The thermal storage system of claim 43, wherein said one or more grids comprise a second grid disposed in said wall structure approximately equidistant between said interior and exterior surfaces thereof, said second grid extending vertically from adjacent an upper edge of said first grid to a point just below said vertical wall's upper surface.
 45. The thermal storage system of claim 44, wherein said first and second grids are thermally linked together for heat transfer therebetween.
 46. The thermal storage system of claim 45, wherein said second plurality of thermally conductive members includes a set of dowels horizontally spaced apart in the longitudinal direction of said footing, each of said dowels extending vertically from a point a selected distance above said footing's lower surface to a point a selected distance into said vertical wall, each of said dowels thermally contacting said thermally conductive strip for heat transfer therebetween.
 47. The thermal storage system of claim 46, wherein said second plurality of thermally conductive members includes a set of dowels horizontally spaced apart in the longitudinal direction of said footing, each of said dowels extending vertically downwardly from thermal contact with said thermally conductive strip, through said footing and into the ground a selected distance.
 48. The thermal storage system of claim 16, wherein said footing additionally comprises at least one longitudinally aligned thermally conductive member extending continuously from one end of said footing to the other.
 49. The thermal storage system of claim 48, wherein said first and second plurality of thermally conductive members and said longitudinally aligned thermally conductive member are metal rods.
 50. A method of storing heat in the ground beneath a building, comprising the steps of: burying at least one length of pipe in the ground below the frost level, said at least one length of pipe configured to receive a working fluid from a heat exchanger, the at least one pipe thermally communicating with the ground below the frost level; forming a longitudinally extending footing in the ground above said at least one length of pipe; supporting a vertical wall on the footing, the vertical wall extending upwardly from the footing to a selected height above grade; sheathing the vertical wall in insulation; lacing the interior of the vertical wall and the footing with thermally communicating heat conducting members, at least some of the heat conducting members extending outwardly from the footing into the ground a selected distance to facilitate heat transfer between the ground and the vertical wall. 